Correctly loaded mag will have the top round that you can push down about 2/3 of the way to almost load another round. I bring this up, since some 30 round bodies, that have anti tilt followers installed, become 29 round mags instead (and so on).

Next, new mag spring will be tight, so will need to insert the correctly loaded mag in the well, and then use the palm of your hand to come up on the bottom of the mag to slap the mag home to seat it against the bottom of the carrier.  In time, the mag spring will loosen up a touch, and will be easier to seat the mag home with just a hard drive upwards instead.  Hence that whole top round being able to move the entire stack down about 2/3 of the way for another round to fit on a correctly loaded mag, is the amount that the bottom of the carrier is going to move the round stack in the mag down as well.  When you over load a mag and the top round can not move down in the mag 2/3 of the way of almost allowing another round to fit, there is not where for the round stack to go as the carrier is trying to force them down during the lock.

As for standard mag release (instead of your CA bullet button catch), end of the catch threads should be flush with the outer face of the button.  If you find that your either 1/2 thread in or out with the catch back in the south side of the receiver channel, remove the catch, and rotate the release button 180* in its receiver channel.  Also, CLP lube the catch parts (including the channel in the receiver) when you are installing the catch.  You have rough anodized parts against rough anodized parts that have not mated into each other yet, and without lube, catch is not going to want to slide open when you are inserting a mag.